1. Field of the Invention
Design for a photographic globe of Earth.
This invention, an Earth Photo Globe, consists of the parts of a globe, a method for the manufacture and preparation of the global photographic emulsion sphere, and several methods for putting appropriate data onto the surface of the sphere with appropriate accuracy.
2. Description of the Prior Art
Existing globes and their limitations.
The current and up until now universal method for making globes of the Earth and other heavenly bodies has been to produce a drawing on a flat surface which is based upon the relevant cartographic information embodied in maps of local surveys. These maps are combined into a larger "global" mapping according to one of several projections, whose geometry describes the appropriate cuts to the flat drawing, so that this drawing may be approximately folded and stretched to fit the spherical surface of the three-dimensional earth model. The National Geographic Society's physical globe using a meridial gore construction is an example of such practice.
The limitations of this method are:
1. Cartographic globes are drawn and as such demand impossible and in some cases (such as the wastes of the Sahara desert) unattainable attention to detail in the process of producing an image of the entire planet. This leads to maps of large areas which must include low resolution and gross inaccuracy somewhere on the surface.
2. The general practice is to make such a drawing on a flat surface and then cut gores to fit around the sphere, gluing and fitting through some mechanical means. The difficulties of aligning these gores simultaneously tends to produce inaccuracies of register at their edges. Two sections will not align up and render any other attempt at high accuracy meaningless.
3. The painstaking process of assembling separate drawings to produce a single image which depends upon the complex integration of large amounts of information means that a globe is difficult to update. To change political boundaries between two countries, for instance, requires that a completely new edition of the globe be produced.
4. Cartographic globes are difficult to reproduce at varying scales, because the mechanics of gluing and fitting require different jigs etc. at different globe sizes.
5. Cartographic globes cannot render multi-spectral information about the Earth, nor can they render continuous data. For instance, to indicate relief contour, lines may be drawn, but there is always a remaining gradient between the contour lines that is impossible to render without obliterating the surface completely.
With the advent of LANDSAT survey and data, the continuation of cartography as the sole means of producing a globe of Earth appears to be an exceptional anachronism. LANDSAT is a NASA high altitude satellite survey of the surface of the earth. Multi-spectral scan using a Vidicon camera provides a continuous output of digital data that covers most of the land of the earth once every nine days. This data is collected at the EROS data center in Sioux Falls, South Dakota and elsewhere, and is in the public domain. The ground resolution of LANDSAT is a picture image or pixel of 79.times.57 m. An individual LANDSAT image surveys an area 100.times.100 nautical miles (=185 km.times.185 km). This means that once every nine days the surface of the earth is encoded into some 36,000,000,000 new bits of information. LANDSAT data is available as digital output (tape), video display (using CRT), and as individually printed photographs. Elaborate and expensive procedures have produced mosaics of individual LANDSAT images to make images of larger areas. For instance, NASA, GE, and National Geographic Society combined to produce in 1976 Space Portrait U.S.A., a photomosaic of some 562 individual LANDSAT images.
Up until this point a globe of LANDSAT images has not been attempted because of the very great difficulties the large amounts of data and requirements of very high resolution present. To make a globe of LANDSAT images (or any other photographic input), one must overcome the following problems:
1. High resolution. To produce a globe on the scale of the current product (diameter of one to two feet), each pixel of LANDSAT data must be represented with an accuracy on the order of 0.0001 inch. This requires exceptional care in mechanical, chemical, optical, and data systems.
2. Precision of register. Once sufficiently accurate data is available to be placed on the globe, it must be placed with at least an equal degree of care. This means that reduced LANDSAT images must align over the entire surface of the globe with again a tolerance of 0.0001 inch.
3. Overlap. Because the original LANDSAT tracking overlaps images from orbit to orbit, and because these neighboring images differ according to time of day, weather conditions etc., where the images overlap there is a certain unwanted visual "noise". Current mosaicing techniques demand a great deal of skill, time and care primarily because of this problem. Any attempt at solving this problem for the entire globe, where thousands of overlap problems will be encountered, must utilize some new and automatic method. Again, the accuracy of this method must also be on the order of 0.0001 inch.
4. Since each LANDSAT image is composed of roughly 6,000,000 pixels or databits, any method of accurately making a globe with this goal of accuracy must utilize some large scale data storage and incorporate it into the printing method.
5. Since so much data is required, the methods for producing the globe must be at very high speeds.
My objective is to produce a very high resolution globe of the earth using the most accurate available photographic data. The ultimate goal is to produce this at a scale of comprehensiveness and precision so that every individual will be able to see both his entire planet (only one hemisphere is visible on a sphere at any one time) and his house (with suitable magnification). Further, I intend to produce this so that the product is of high quality and competitive in price with existing products in the field.
After surveying the current state of the art, I have concluded that this ultimate objective is not attainable at the present time. In face, in several related fields, it appears that the present limits to data input, resolution of image, and resolution and mechanical registration in production are all too gross, perhaps by an order of magnitude. This still will produce a product of far greater accuracy than anything currently attainable. The globe thus produced will be able to carry each individual pixel of LANDSAT data, which is of course already too gross to distinguish individual buildings.
Whatever the limitation of technology for scale, the method will remain the same when certain technical problems are solved and higher resolutions are available. Using a rule of thumb common in the microelectronics industry, which is concerned with many of the problems relating to this design, one may expect that the appropriate resolution will double every year or so. Thus such resolution may be available soon.